Early defibrillation by emergency medical personnel has been shown to improve survival in patients suffering from out-of-hospital cardiac arrest with ventricular fibrillation. Due to organisational differences it is difficult to compare results in various studies. Comparison of studies has been simplified by introduction of the Utstein template. After introduction of an early defibrillation program in Hamburg, we compared the patients being treated with early defibrillation by emergency medical technicians (EMTs) with patients being defibrillated by physicians in an out-of-hospital emergency service in a prospective study. All patients suffered from non EMT-witnessed ventricular fibrillation of cardiac origin. During 1 year, 103 patients were analyzed with respect to survival rate and quality of life. Of the 53 patients in the early defibrillation group (G1) 11 regained a palpable pulse at physicians' arrival, whereas all patients of the control group (G2) showed ventricular fibrillation. More patients treated with early defibrillation regained sinus rhythm without antiarrhythmics in the prehospital phase (G1: n=43 (86%); G2: n=32 (60%); P<0.05) and had a shorter in-hospital stay (G1: median, 23 days; range 5-51 days; G2: median 39, range 15-88 days; P<0.05). Twelve patients in G1 and 16 in G2 were discharged from hospital. The survival rate was similar in both groups (after 6 months G1: n=12; G2: n=14, after 12 months G1: n=10; G2: n=13 and after 24 months G1: n=9; G2: n=10), and the quality of life according to Glasgow-Pittsburgh Cerebral Performance Category (CPC) and Overall Performance Category (OPC) scores also was comparable between groups. We conclude that early defibrillation provides a higher incidence of return of a spontaneous circulation, a reduced need for antiarrhythmics and shorter in-hospital treatment times in patients with out-of-hospital ventricular fibrillation.